Metabolism of non-steroidal anti-inflammatory drugs (NSAIDs) by Streptomyces griseolus CYP105A1 and its variants

In the field of drug development, technology for producing human metabolites at a low cost is required. In this study, we explored the possibility of using prokaryotic water-soluble cytochrome P450 (CYP) to produce human metabolites. Streptomyces griseolus CYP105A1 metabolizes various non-steroidal anti-inflammatory drugs (NSAIDs), including diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, meclofenamic acid, and ibuprofen. CYP105A1 showed 4′-hydroxylation activity towards diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, and meclofenamic acid. It should be noted that this reaction specificity was similar to that of human CYP2C9. In the case of mefenamic acid, another metabolite, 3′-hydroxymethyl mefenamic acid, was detected as a major metabolite. Substitution of Arg at position 73 with Ala in CYP105A1 dramatically reduced the hydroxylation activity toward diclofenac, flufenamic acid, and ibuprofen, indicating that Arg73 is essential for the hydroxylation of these substrates. In contrast, substitution of Arg84 with Ala remarkably increased the hydroxylation activity towards diclofenac, mefenamic acid, and flufenamic acid. Recombinant Rhodococcus erythrocyte cells expressing the CYP105A1 variant R84A/M239A showed complete conversion of diclofenac into 4′-hydroxydiclofenac. These results suggest the usefulness of recombinant R. erythropolis cells expressing actinomycete CYP, such as CYP105A1, for the production of human drug metabolites.     

Glucuronidation of fenamates: kinetic studies using human kidney cortical microsomes and recombinant UDP-glucuronosyltransferase (UGT) 1A9 and 2B7

Mefenamic acid, a non-steroidal anti-inflammatory drug (NSAID), is used commonly to treat menorrhagia. This study investigated the glucuronidation kinetics of flufenamic, mefenamic and niflumic acid using human kidney cortical microsomes (HKCM) and recombinant UGT1A9 and UGT2B7. Using HKCM Michaelis-Menten (MM) kinetics were observed for mefenamic (K(m)(app) 23 microM) and niflumic acid (K(m)(app) 123 microM) glucuronidation, while flufenamic acid exhibited non-hyperbolic (atypical) glucuronidation kinetics. Notably, the intrinsic renal clearance of mefenamic acid (CL(int) 17+/-5.5 microL/minmg protein) was fifteen fold higher than that of niflumic acid (CL(int) 1.1+/-0.8 microL/minmg protein). These data suggest that renal glucuronidation of mefenamic acid may result in high intrarenal exposure to mefenamic acyl-glucuronide and subsequent binding to renal proteins. Diverse kinetics were observed for fenamate glucuronidation by UGT2B7 and UGT1A9. Using UGT2B7 MM kinetics were observed for flufenamic (K(m)(app) 48 microM) and niflumic acid (K(m)(app) 135 microM) glucuronidation and atypical kinetics with mefenamic acid. Similarity in K(m)(app) between HKCM and UGT2B7 suggests that UGT2B7 may be the predominant renal UGT isoform catalysing niflumic acid glucuronidation. In contrast, UGT1A9 glucuronidation kinetics were characterised by negative cooperativity with mefenamic (S(50) 449 microM, h 0.4) and niflumic acid (S(50) 7344 microM, h 0.4) while atypical kinetics were observed with flufenamic acid. Additionally, potent inhibition of the renal glucuronidation of the UGT substrate 'probe' 4-methylumbelliferone by flufenamic, mefenamic and niflumic acid was observed. These data suggest that inhibitory metabolic interactions may occur between fenamates and other substrates metabolised by UGT2B7 and UGT1A9 in human kidney.     

Binding of nonsteroidal anti-inflammatory agents and their effect on binding of racemic warfarin and its enantiomers to human serum albumin

The binding of racemic warfarin, its enantiomers, and several nonsteroidal anti-inflammatory agents to human serum albumin was investigated by equilibrium dialysis at 4 degrees C in pH 7.4 phosphate buffer. The primary binding constant for the S(-) enantiomer of warfarin was approximately two times greater than the corresponding binding of the R(+) enantiomer. The effect of azapropazone, phenylbutazone, naproxen, ibuprofen, mefenamic acid, and tolmetin on the binding of racemic warfarin and its enantiomers was studied. Warfarin was displaced by all of the nonsteroidal anti-inflammatory agents except tolmetin. Azapropazone caused the largest displacement of warfarin (39 to 46% free warfarin versus 2.5 to 6% free warfarin without competing drug), followed by phenylbutazone (23 to 43% free warfarin), naproxen (9 to 24% free warfarin), mefenamic acid (5 to 11.5% free warfarin), and ibuprofen (5 to 9% free warfarin). Azapropazone and phenylbutazone competed with warfarin for the same primary binding site on the albumin molecule. Naproxen appeared to affect warfarin binding at both primary and secondary sites. Ibuprofen and mefenamic acid interfered with the binding of warfarin at its secondary sites. In contrast to the other drugs studied, tolmetin caused an increase in the primary binding constant of warfarin. Structural analysis indicated that a common feature of those compounds which primarily bind at the warfarin site is a hydrophobic area bearing a widely delocalized negative charge.     

Influence of non-steroid anti=inflammatory drugs (NSAIDd) on hepatic tyrosine aminotransferase (TA) activity in rats in vitro and in vivo.

Indomethacin, flufenamic acid, mefenamic acid, gold sodium thiosulphate and ibuprofen were found to be inhibitors of hepatic TA in vitro. The type of inhibition was competitive relative to l-tyrosine; apparent K_i values ranged from 0.7 × 10^?4 to 1.18 × 10^?3 M. Several other NSAIDs did not, or poorly, inhibit TA at concentrations of ≤ 10^?3M. In intact rats, TA activity was stimulated 18-fold by pretreatment with mefenamic acid, 7-fold by dimethylsulfoxide and ibuprofen, 5-fold by acetylsalicylic and flufenamic acid, and doubled by benzydamine, amidopyrine, sodium salicylate and gold sodium thiosulphate. Indomethacin was somewhat less effective. Drug dosage was 20 per cent of the acute p.o. LD₅₀, three times with 12-hourly intervals. Phenylbutazone, chloroquine and cyclophosphamide significantly increased TA activity also, though the dose was smaller relative to LD₅₀. Adrenalectomy decreased the drug effects in almost all cases. Equi-toxic i.p. or p.o. doses of acetylsalicylic acid were equi-effective in intact rats. The action was dose-dependent and could be observed at a therapeutic dose. Elevated TA activities were determined up to 28 hrs after the last drug administration. Concomitant administration of glucose did not suppress the effect of mefenamic acid. The findings led to the following hypothesis: TA stimulation by NSAIDs depends on the actions of endogenous corticosteroids and, possibly, cyclic 3',5'-AMP. Similar processes might play a role in the anti-inflammatory mechanism of NSAIDs.     

Formulation and evaluation of reconstitutable suspensions containing ibuprofen-loaded Eudragit microspheres

The objective of this work was to develop and evaluate reconstitutable suspensions of ibuprofen-loaded microspheres prepared with an acrylic polymer (Eudragit RS-PM). The microspheres were prepared by the quasi-emulsion solvent diffusion technique. To prepare reconstitutable suspension formulation, the microspheres used had a mean particle size of 316.6 microm and 99.8% loading efficiency. Xanthan gum was chosen as the suspending agent for the suspension formulations. D-sorbitol was used to impart palatability of suspensions. The amount of D-sorbitol affected sedimentation volume and redispersibility properties of suspensions. The highest improving effect was shown with 20.0% and 25.0% of D-sorbitol concentrations. It was observed that dispersion media of suspensions showed non-Newtonian flow characteristics. To ensure minimum drug leakage from the microspheres into the suspension, the pH was buffered at 3.60 using citrate buffer. The ibuprofen content calculated from the suspended microspheres was consistent with that from microspheres alone. This result indicated that no leakage of drug occurred from the microspheres in the suspension on storage. Moreover, the same release rate of ibuprofen from the microspheres suspension and microspheres alone indicated that the suspension medium studied did not affect the property of drug release. This study suggested that stable suspensions of ibuprofen-loaded microspheres could be formulated with 0.6% w/v xanthan gum by the addition of 20% w/v D-sorbitol.     

Contribution of cytochrome P450 and UDT-glucuronosyltransferase to the metabolism of drugs containing carboxylic acid groups: risk assessment of acylglucuronides using human hepatocytes

Abstract

1.?In order to evaluate the inhibition activity of 1-aminobenzotriazole (ABT) and (?)-borneol (borneol) against cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT), the substrates of these metabolic enzymes were incubated with ABT and borneol in human hepatocytes. We found that 3?mM ABT and 300?μM borneol were the most suitable experimental levels to specifically inhibit CYP and UGT.

2.?Montelukast, mefenamic acid, flufenamic acid, diclofenac, tienilic acid, gemfibrozil, ibufenac and repaglinide were markedly metabolized in human hepatocytes, and the metabolism of gemfibrozil, mefenamic acid and flufenamic acid was inhibited by borneol. With regard to repaglinide, montelukast, diclofenac and tienilic acid, metabolism was inhibited by ABT. Ibufenac was partly inhibited by both inhibitors. Zomepirac, tolmetin, ibuprofen, indomethacin and levofloxacin were moderately metabolized by human hepatocytes, and the metabolism of zomepirac, ibuprofen and indomethacin was equally inhibited by both ABT and borneol. The metabolism of tolmetin was strongly inhibited by ABT, and was also inhibited weakly by borneol. Residual drugs, telmisartan, valsartan, furosemide, naproxen and probenecid were scarcely metabolized.

3.?Although we attempted to predict the toxicological risks of drugs containing carboxylic groups from the combination chemical stability and CL_int via UGT, the results indicated that this combination was not sufficient and that clinical daily dose is important.     

Effect of some antirheumatics on connective tissue components.

The effects of a number of classical and modern antirheumatics on the biosynthesis of glycosaminoglycans and collagen were studied comparatively. The experimental results indicate that the antirheumatics deeply affect the metabolism of the main components of connective tissue. With regard to the methods used for testing, it may be stated that phenylbutazone, flufenamic acid, ibuprofen, mefenamic acid and trimetazone belong to the most effective of the entire series of antirheumatics tested.     

Comparison of the effects of fenamates on Ca-activated chloride and potassium currents in rabbit portal vein smooth muscle cells.

1. The perforated patch and conventional whole-cell recording techniques were used to study the action of flufenamic, mefenamic and niflumic acid on calcium-activated chloride and potassium currents in rabbit portal vein smooth muscle cells. 2. In K-conditions at a holding potential of -77 mV flufenamic acid and mefenamic acid decreased the amplitude of spontaneous transient inward currents (STICs, calcium-activated chloride currents, ICl(Ca)) in a concentration-dependent manner. The potency sequence was niflumic > flufenamic > mefenamic acid. 3. At -77 mV 1 x 10(-5) M flufenamic acid increased the STIC exponential decay time constant (tau). At higher concentrations the STIC decay was described by 2 exponentials with an initial decay (tau f) faster than the control tau value and a second exponential (tau s) which had a time constant slower than the control tau value. Low concentrations of mefenamic acid had no effect or decreased the tau value whereas in higher concentrations biphasic currents were recorded. 4. In K-free conditions the inhibitory effect of both flufenamic and mefenamic acid on STIC amplitude was greater at +50 mV compared to -50 mV, showing that the effect of these agents was voltage-dependent. 5. In cells held at 0 mV in K-containing conditions the fenamates reduced both the frequency and amplitude of spontaneous transient outward currents (STOCs, calcium-activated potassium currents, IK(Ca)). The concentration range to produce these effects was higher than that to decrease STIC amplitude and the potency sequence was flufenamic > niflumic > or = mefenamic acid. 6. All these compounds in concentrations greater than 5 x 10(-5) M evoked a 'noisy' potassium current at 0 mV which reached a maximum after approximately 3 min. This current was readily reversible on washout of the drug and could be elicited several times in the same cell. The current-voltage relationship of the fenamate-evoked current exhibited pronounced outward rectification characteristic of IK(Ca). 7. The current evoked by 2 x 10(-4) M flufenamic acid and 5 x 10(-4) M niflumic acid was not affected by 1 x 10(-5) M glibenclamide but was markedly inhibited by 1 x 10(-3) M tetraethylammonium. Furthermore, large currents were activated by flufenamic and niflumic acid in the presence of caffeine and cyclopiazonic acid (an inhibitor of the sarcoplasmic reticulum Ca-ATPase) to deplete intracellular Ca-stores. 8. Conventional whole-cell recording was performed with pipette solutions in which the ability to buffer changes in intracellular calcium was varied by altering the concentration of the calcium chelator (2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA). Flufenamic acid (2 x 10(-4) M) and niflumic acid (5 x 10(-4) M) both evoked large outward currents when recordings were made with either 1 x 10(-4) M or 1 x 10(-2) M BAPTA. Furthermore, bathing the cells in nominally calcium-free extracellular solution did not reduce the amplitude of the evoked currents. 9. It is concluded that both flufenamic and mefenamic acid inhibit ICl(Ca) by a mechanism similar to niflumic acid, possibly open channel blockade. Furthermore, at concentrations greater than 5 x 10(-5) M all three fenamates inhibited STOC activity and evoked directly an outward current which resembled IK(Ca).     

Fenamates and the potent inhibition of human liver phenol sulphotransferase

1. The inhibition of the human liver phenol sulphotransferase (HL-PST) and catechol sulphotransferase (HL-CST) by five fenamates has been studied and the activities of HL-PST and HL-CST were measured with 4-nitrophenol and dopamine as substrates, respectively. 2. The IC50 for inhibition of HL-PST were 0.02 microM (mefenamic acid); 0.12 microM (tolfenamic acid); 0.28 microM (niflumic acid); 0.87 microM (meclofenamic acid) and 1.50 microM (flufenamic acid). 3. HL-CST was less susceptible than HL-PST to the inhibition by fenamates and the IC50 for HL-CST were 36 microM (tolfenamic acid); 70 microM (flufenamic acid); 76 microM (mefenamic acid); 180 microM (niflumic acid) and 185 microM (meclofenamic acid). 4. The ratios of the IC50 for HL-CST:HL-PST were drug-dependent and ranged from 47 (flufenamic acid) to 3800 (mefenamic acid). Mefenamic acid is a relatively potent and selective inhibitor of HL-PST. 5. The IC50 for HL-PST obtained with mefenamic acid was three orders of magnitude lower than the peak plasma concentration of this drug after an oral dose of 0.5 g. Accordingly, mefenamic acid should impair sulphation in vivo.     

Relaxant effect of aspirin-like drugs on isolated guinea pig tracheal chain.

The interrelation of the inhibitory effect of aspirin-like drugs on the resting tonus of tracheal chain in guinea pigs, arachidonic acid-induced contraction in rat stomach fundus strips and bradykinin-induced bronchoconstriction in guinea pigs in vivo was investigated. All the drugs tested produced a dose-related inhibitory action on the resting tonus of the tracheal chain in comparatively low doses. Diclofenac was the most potent of all the drugs and was equal in activity to isoproterenol, followed in descending order by flufenamic acid, mefenamic acid, indomethacin, ibuprofen, phenylbutazone, oxyphenbutazone and aspirin. These aspirin-like drugs also inhibited arachidonic acid-induced contraction in rat stomach fundus strips. A highly significant correlation was observed between the potency of inhibition of the arachidonic acid-induced contraction and the relaxant effect on the tracheal chain. Moreover, the drugs antagonized bradykinin-induced bronchoconstriction in guinea pigs in vivo and the order of potency roughly paralleled that of the tracheal chain. These results suggest that the aspirin-like drugs produce a reduction in resting tonus of the isolated guinea pig tracheal chain by inhibition of intramural biosynthesis of prostaglandin endoperoxides.     

Protection by paracetamol against various gastric irritants in the rat

Four nonsteroid anti-inflammatory drugs (NSAID), indomethacin, phenylbutazone, ibuprofen, and glafenine, caused erosions in the rat stomach in a dose-dependent manner. Paracetamol, which has been shown to protect against the gastric erosive activity of aspirin, reduced the gastric toxicity of indomethacin but was ineffective against the erosive activity of phenylbutazone and glafenine. Only the high erosion score of a large dose of ibuprofen was partly decreased by paracetamol. The gastric damaging effects of necrotizing concentrations of ethanol and sodium hydroxide were strongly reduced by paracetamol, but the erosive activity of hydrochloric acid was only slightly decreased by paracetamol. Thus, although paracetamol protected the gastric mucosa against various noxious agents, this drug was not able to protect against every type of gastric damage. Paracetamol might be protective by stimulating the biosynthesis of prostaglandins in the stomach wall.     

Infrared studies of the polymorphic states of the fenamates

Infrared spectroscopy has been used to characterize the polymorphic purity as well as to study the thermal conversion of three of the more common fenamates between their different crystalline forms via measuring changes in the NH stretch region that occur between 3300 and 3350 wavenumbers. Shifts in band frequency for mefenamic acid result from differences in internal hydrogen bonding between the NH group and either the carbonyl or hydroxyl groups of the acid moiety. Due to out-of-plane rotations about the central N-C(ring2) bond additional polymorphic states have been suggested for flufenamic and tolfenamic acids. Rates of conversion are given for flufenamic, mefenamic, and tolfenamic acids at temperatures between 85 and 160 degrees C depending on the polymorphic transition for a particular analyte. Subsequently, these rates are used to calculate the activation energy for the observed polymorphic transition. Values of 71.6, 49.0, and 50.8 kcal/mol are obtained respectively for (1) the polymorph I to II transition of mefenamic acid, (2) the polymorph I to II transition of tolfenamic acid, and (3) the polymorph III to I transition of flufenamic acid.     

The effect of taste masking agents on in situ gelling pectin formulations for oral sustained delivery of paracetamol and ambroxol

The aim of this study was to examine the influence of polyhydric alcohols (taste masking agents) on the rheological properties of in situ gelling pectin formulations and on the in vitro and in vivo release of paracetamol and ambroxol from these formulations. Gelation of orally administered pectin solutions containing calcium in complexed form occurred on release of calcium in the acidic environment of the stomach. Inclusion of 10% (w/v) sorbitol in 2% (w/v) pectin sols reduced the viscosity and ensured Newtonian flow properties. Xylitol and mannitol in similar concentrations were less effective in reducing viscosity; sucrose increased viscosity and caused non-Newtonian flow. The in vitro release of paracetamol from 2% (w/v) pectin gels formulated with 10% (w/v) of sorbitol, erythritol, xylitol or mannitol, and of ambroxol from 2% (w/v) pectin gels containing 10% (w/v) sorbitol, followed diffusion-controlled kinetics. Pectin gels (2%, w/v) containing sorbitol (10%, w/v) sustained the release of paracetamol in the rat stomach and bioavailabilities of approximately 90% of those from an orally administered paracetamol syrup were achieved. Sustained release of ambroxol from in situ gelling formulations was achieved with pectin concentrations of 1.5 and 1% (w/v) and a sorbitol concentration of 10% (w/v).     

Section 2 The comparison of four non-steroidal antirheumatic agents in the treatment of rheumatic diseases

Summary

A comparative open study was made of the effectiveness of four antirheumatic agents in the treatment of 69 hospitalised patients with rheumatic diseases who had failed to respond satisfactorily to previous therapies. Simple subjective and objective assessments showed that approximately half the patients treated with ibuprofen, oxyphen-butazone or mefenamic acid showed improvement, but that fewer did so with flufenamic acid. Full therapeutic effect of the drugs was evident in approximately 3 weeks.     

Simultaneous determination of non-steroidal anti-inflammatory drugs in river water samples by liquid chromatography-tandem mass spectrometry using molecularly imprinted polymers as a pretreatment column

A restricted access media-molecularly imprinted polymer (RAM-MIP) for flufenamic acid has been developed for the simultaneous determination of non-steroidal anti-inflammatory drugs (NSAIDs) in river water samples. The RAM-MIP was prepared using 4-vinylpyridine and ethylene glycol dimethacrylate as a functional monomer and cross-linker, respectively, by a multi-step swelling and polymerization method followed by a surface modification technique. The RAM-MIP for flufenamic acid showed excellent molecular recognition abilities for flufenamic acid and mefenamic acid, and moderate molecular recognition abilities for indomethacin, etodolac and ketoprofen. The simultaneous determination of NSAIDs (mefenamic acid, indomethacin, etodolac and ketoprofen) in river water samples was carried out by LC-MS/MS using the RAM-MIP for flufenamic acid as a pretreatment column. The concentrations of mefenamic acid, indomethacin and etodolac in river water samples were determined to be 0.4, 0.7 and 0.3ng/L, respectively, while ketoprofen was below the limit of quantitation.     

Oral antipyretic therapy: Evaluation of the N-aryl-anthranilic acid derivatives mefenamic acid,tolfenamic acid and flufenamic acid

Summary The antipyretic activity of three N-aryl-anthranilic acid derivatives, mefenamic acid, tolfenamic acid and flufenamic acid, was compared and their optimal antipyretic dose determined in a trial in 87 children (aged 5 months to 15 years), who suffered from infections and fever exceeding 38.5°C. Tolfenamic acid proved to be the most potent antipyretic agent of the three drugs; it was eight times more powerful than mefenamic acid and three times more powerful than flufenamic acid. The optimal antipyretic doses were: mefenamic acid 4 mg/kg, tolfenamic acid 0.5 mg/kg and flufenamic acid 1.5 mg/kg. It is evident that the antipyretic activity of these anthranilic acid derivatives is even greater than their antirheumatic effect, the difference being most noticeable in the case of tolfenamic acid.     

Dysmenorrhoea and prostaglandins: pharmacological and therapeutic considerations

Primary dysmenorrhoea is characterised by painful menstrual cramps which appear to have no macroscopically identifiable pelvic pathology. 50% of postpubescent females suffer from dysmenorrhoea, and 10% are incapacitated for 1 to 3 days each month. Many of these patients have an increased synthesis of prostaglandins in their endometrial tissue with increased prostaglandin release in the menstrual fluid. The increased amount of prostaglandins induces incoordinate hyperactivity of the uterine muscle resulting in uterine ischaemia and pain. Recent clinical and laboratory studies have shown that many of the non-steroidal anti-inflammatory drugs such as ibuprofen, naproxen, flufenamic acid, mefenamic acid and indomethacin are capable of relieving primary dysmenorrhoea. These drugs are inhibitors of the prostaglandin synthetase enzymes which are necessary for prostaglandin biosynthesis. Thus, with ibuprofen it has been shown that clinical relief of the dysmenorrhoeic symptoms accompanies the reduction of menstrual fluid prostaglandins. With the oral contraceptive pill there is good relief of primary dysmenorrhoea, significant decrease in menstrual fluid prostaglandins, but no reduction in menstrual fluid volume; this suggests that the reduction in prostaglandins is secondary to the inhibition of endometrial growth and development. In some forms of secondary dysmenorrhoea elevated prostaglandin levels have been implicated. However, the evidence is less conclusive for dysmenorrhoea secondary to endometriosis and uterine myomas than for dysmenorrhoea associated with intrauterine devices. With the intrauterine device, prostaglandin synthetase inhibitors such as flufenamic acid, ibuprofen and naproxen are able not only to relieve dysmenorrhoea but also to reduce menstrual blood loss to normal levels. Thus, the use of appropriately selected prostaglandin synthetase inhibitors can offer effective relief from the miseries of some types of dysmenorrhoea with subsequent restoration of normal daily activities.     

Stereoselective Disposition of Suspensions of Conventional and Wax-matrix Sustained Release Ibuprofen Microspheres in Rats

Purpose. The aim of the study is to evaluate stereoselective in vivo disposition of suspensions of conventional and wax-matrix sustained release ibuprofen microspheres in rats. Methods. Male wistar rats were dosed IV with 20 mg/kg, or orally with conventional suspension, and three suspension formulations of sustained release microspheres (having three different particle sizes) of racemic ibuprofen. Blood samples were analyzed stereoselectively by reverse phase HPLC. Results. The mean C_max for (S)- and (R)- ibuprofen decreased with increased particle size of the drug or microspheres in the suspension dosage forms, while the T_max increased with increased particle size. The mean S/R ratio (AUC_0–48) of the suspensions decreased with increase in particle size of the drug or microspheres and these ratios (for both conventional and sustained formulations) were higher than that of the IV, an indication of presystemic inversion. Decrease in the ratios with increased particle size is suggestive of formulation dependent inversion. The plasma concentration-time data of the sustained release formulations showed bimodal profiles, irrespective of the particle size of the microspheres. The second peak observed after 8 hours is indicative of colonic absorption. Conclusions. Stereoselective disposition of ibuprofen microspheres showed higher bioavailability compared to the conventional suspension. Bimodal disposition is influenced by dosage form while presystemic inversion is both site-specific, and dosage form dependent.     

Influence of limonene and laurocapram on percutaneous absorption of nonsteroidal anti-inflammatory drugs.

The promoting effect of cyclic monoterpenes, 1% limonene (CAS 5989-27-5) and 1% cineole (CAS 470-82-6), on percutaneous absorption of nonsteroidal anti-inflammatory drugs was investigated in the rats. Compared with 1% laurocapram, drug absorption from the gel ointments was significantly more enhanced by addition of 1% limonene, while without any enhancer only ibuprofen penetrated across the skin in the limited amount. When using formulation with propylene glycol or 50% propylene glycolethanol solution, instead of carboxyvinyl polymer gel, percutaneous absorption significantly decreased and neither limonene nor cineole or laurocapram were capale to promote percutaneous absorption of flufenamic acid to sufficient serum level. Cineole and limonene were also evaluated in permeation experiments in vitro. Enhancement ability of limonene in the gel oinment was approximately 5 times higher comparing with enhancement ratio of cineole, while in 100% propylene glycol enhancement ability of both cyclic monoterpenes was equal. Good correlation was observed between in vivo and in vitro experiments. Evaluation of solubility proved that in the gel ointment simulated as water-ethanol solution were relatively best condition for percutaneous absorption of flufenamic acid when comparing with propylene glycol or 50% propylene glycol-ethanol solution.     

Antagonism by mefenamic and flufenamic acids of the bronchoconstrictor action of kinins in the guinea-pig

In the guinea-pig, N-(2,3-xylyl)anthranilic acid (mefenamic acid) and N-(α,α,α-trifluoro-m-tolyl)anthranilic acid (flufenamic acid), two new anti-inflammatory agents, antagonize bronchoconstriction, but not hypotension, produced by kinins. They do not reduce bronchoconstrictor responses to acetylcholine, histamine or 5-hydroxytryptamine. The antibradykinin potencies of mefenamic and flufenamic acids approximately equal that of acetylsalicylic acid when given intravenously and of phenylbutazone when given into the duodenum. After administration of mefenamic and flufenamic acids, the bronchoconstrictor response can be restored by higher doses of bradykinin. The quantitative relationship between the intravenous dose of sodium mefenamate or flufenamate and the dose of bradykinin needed to surmount either antagonist in bronchial muscle fulfils the requirements for competitive antagonism. Antagonism by calcium acetylsalicylate can also be surmounted with higher doses of bradykinin, but in this instance the relationship of antagonist to agonist fulfils requirements for competitive antagonism only at the lower part of the dose range.